An electron beam irradiation apparatus conventionally used for sterilization in a container with a narrow neck includes: a vacuum chamber; an electron generator provided in the vacuum chamber; and a cylindrical nozzle member that is extended from the vacuum chamber so as to be inserted into the container from the neck and has exit windows on the distal end of the nozzle member, the exit windows being provided for emission of electron beams generated by the electron generator (For example, Patent Literature 1). As shown in FIG. 3, a nozzle member 14 is inserted into a container 18 from the neck of the container, and then electron beams are emitted from the distal end of the nozzle member 14 to clean the inside of the container 18.
Although electron beams are widely emitted from the exit windows provided on the distal end of the nozzle member 14, a reduction in electron dose may limit a sterilisation range and thus the exit windows need to be brought close to the bottom of the container 18. This requires the length of the nozzle member 14 to be substantially equal to the height of the container 18. If the container 18 is tall, the nozzle member 14 may be 30 cm to 40 cm in length. Moreover, the nozzle member 14 needs to have an outside diameter (e.g., about 10 mm) so as to be loosely fit into the mouth of the container 18. Thus, the nozzle member 14 requires a slender shape. Furthermore, in order to stably emit electron beams into the container 18, electron beams need to pass through in an elongated shape in the nozzle member 14, that is, an electron beam trajectory needs to be elongated in the nozzle member 14.